Glaucoma is a significant health problem effecting about three million people in the United States alone. It is a leading cause of blindness, with about ten percent of the treated cases still resulting in blindness. In addition, estimates assert that only about half of the cases are diagnosed, much less treated. While treatments are effective for lessening some of the symptoms of glaucoma, such as vision loss, there is currently no cure for glaucoma.
Because high intraocular pressure is the most common risk factor for glaucoma, many treatments attempt to lower the intraocular pressure using either drugs or surgery to open the trabecular network and drainage canals to drain fluid from the eye, or to slow fluid production in the eye.
Primary open-angle glaucoma (POAG) and angle closure glaucoma are the two most common types of glaucoma. Current surgical treatments for POAG include laser eye surgery and traditional eye surgery. One type of laser surgery is selective laser trabeculoplasty (SLT), using a laser beam to open select areas of the trabecular meshwork of the eye and thereby improve fluid flow out of the eye. Another type of laser surgery is argon laser trabeculoplasty (ALT), using a laser beam to open blocked or closed drainage canals and thereby improve fluid flow out of the eye. Drugs may be applied in combination with these therapies.
Current treatments for angle closure glaucoma include laser cyclophotocoagulation, which treats the ciliary body and thus reduces the production of fluid and decreasing the fluid volume to be removed.
Conventional surgery is generally used only after medication and laser surgery has failed or in an emergency situation. The most common procedure is filtering microsurgery, also known as trabeculectomy. One or more small incisions are made in the sclera, through which fluid flows out of the eye and is absorbed by the blood. A flap of tissue is left to cover the incisions.
While effective, patients may not tolerate surgery or may have factors for which surgery may not be effective (e.g., patients with neovascular glaucoma, glaucoma associated with uveitis, prior history of a failure with a filtering procedure, or a glaucoma patient under the age of 30). Such patients may require a tube shunt device to be implanted through which fluid drains from the eye. Examples of such devices include Ahmed™ glaucoma valves (New World Medical, Inc., CA) Baerveldt® glaucoma implants (Advanced Medical Optics, Inc., Santa Ana Calif.), or Molteno® glaucoma implants (Molteno Ophthalmic Ltd., Dunedin, New Zealand).
Shunt implant surgery requires multiple steps and difficulties exist with current devices. Moreover, it would be desirable to control of dispersion of the fluid that is removed from the eye, that is, to regulate its outflow. Failure to adequately regulate fluid release can lower intraocular pressure too rapidly, leading to a “soft” eye. In addition, cytokines in the aqueous humor can leak and accelerate the inflammatory process possibly, leading to scarring. Therefore, other devices and methods of using the devices are desirable.